Fiber glass mats are used as a facing material to reinforce flat insulation panels of polyurethane foam. However the glass mats or mesh have never been engineered to comply with the needs of the industry to reinforce curved profiles of architectural mouldings.
An architectural moulding comprises a decorative strip that has the appearance of being made of solid plaster or solid cement when installed on a building. The moulding comprises a light weight polymeric foam core having a surface topography shaped with decorative, curved architectural features to provide a decorative appearance, and a surface layer of cementitious material to provide an exterior finish coating over the curved architectural features. For example, the finish coating comprises plaster for indoor use or Portland cement for outdoor use.
Moreover, as new architectural profiles are designed and built, existing mesh products have been unable to adapt to a new profile, such that the mesh will tend to lift away from the surface of the profile, particularly at an abrupt radius of curvature or at a series of reversing radii of curvature. Manufacturers deal with this problem by delaying or interrupting the process of applying the cementitious coating and relying on hand work to press down the uplifted mesh, or by applying a localized amount of adhesive to re-attach the mesh against the profile and waiting for the adhesive to cure to a tenacious adherent state. What results is a delay in manufacturing, as well as, the increased probability of producing a defective part in which the mesh is insufficiently attached to the profile, or may even protrude out from the cementitious coating.
An architectural moulding has a light weight foam core, typically an expanded high density polystyrene, in the form of an elongated beam of substantial length, eight feet or two meters, for example, and of substantially large aspect ratio of length versus transverse dimensions. The cross sectional dimensions are thin relative to the length. Thus, the architectural moulding is vulnerable to sagging, by beam deflection, under the influence of its own weight and length when transported and handled prior to installation on a building. Sagging applies stress that tends to crack the cementitious coating when placed under tension. Sagging further applies stress that tends to separate the cementitious coating from the foam core. Ambient temperature changes further contribute to such cracking and/or separation due to a difference in thermal expansion rates of the foam core and the cementitious coating. Thus, to restrain sagging and undue thermal expansion and contraction of the foam core relative to the cementitious coating, a reinforcement mesh is applied to the foam core before the cementitious coating is applied. This requires bending of the mesh to conform to and against the decorative, curved profile of the architectural features on the foam core.
The mesh carries an adhesive on one side of the mesh to adhere the mesh to the profile. However, the mesh when bent tends to undergo elastic strain, which stores resilient spring energy in the bent yarns of the mesh. The stored spring energy thereby provides an impetus to the bent mesh to return to its former unbent orientation, a behavior referred to as undergoing shape memory recovery. The elastic strain and tendency for shape memory recovery lifts the mesh away from the profile of the polystyrene core, and spring biases the adhesive to give way under tension and release the mesh from adherence to the profile. Moreover, a mesh complying with an industry standard specification for minimum areal weight tended to undergo significant strain and shape memory recovery, which lifted the mesh from the surface of the architectural moulding core.
Over the mesh is applied a coating of a proprietary plaster, concrete, or other cementitious material to a thickness of about 0.13 inches, 3.3 mm., which bonds to the mesh and penetrates through openings through the mesh to bond with the foam core. Given the weight and brittle nature of the cementitious coating, the softness of the polystyrene core and the beam length and large aspect ratio of the moulding, it is easy to foresee that its own weight and length would induce a bending moment capable of cracking the coating. Moreover, given the length of the moulding and its construction of dissimilar materials, it is understandable that cracking of the cementitious material would occur due to differences in thermal expansion rates of the dissimilar materials. The reinforcement mesh serves to resist the beam deflection and bear the thermal expansion loads. However, prior to the invention, the reinforcement mesh was prone to lifting away from the polystyrene core due to a tendency for shape memory recovery.
What the moulding industry requires in terms of mesh behaviors are, for the mesh to bend and conform to and against a profile of curved architectural features on an architectural moulding, and for the mesh to remain substantially where it was placed and remain adhered to the profile over the passage of time, at least until the cementitious coating is applied and dried to a stable rigid state. Further, compliance of a mesh with an industry accepted standard for a minimum areal weight is desirable.